The
pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp (
fungal fruiting body) that supports a spore-bearing surface, the hymenium. The hymenium (
hymenophore) may consist of
lamellae, tubes, or teeth, on the underside of the pileus. A pileus is characteristic of
agarics,
boletes, some
polypores,
tooth fungi, and some
ascomycetes.